feat(flutter): implement build runner widget analyzer

Author: abhaysood

flutter/example/build.yaml

@@ -0,0 +1,6 @@
+targets:
+  $default:
+    builders:
+      msr_build:widget_analyzer:
+        options:
+          widgets_output_path: lib/src/msr/msr_widgets.g.dart

flutter/example/lib/main.dart

@@ -2,27 +2,26 @@ import 'dart:async';
 
 import 'package:flutter/material.dart';
 import 'package:measure_flutter/measure_flutter.dart';
+import 'package:measure_flutter_example/src/msr/msr_widgets.g.dart';
 import 'package:measure_flutter_example/src/screen_main.dart';
 
+
 Future<void> main() async {
   await Measure.instance.init(
     () => runApp(MeasureWidget(child: MyApp())),
     config: const MeasureConfig(
-        enableLogging: true,
-        trackScreenshotOnCrash: true,
-        trackHttpHeaders: true,
-        trackHttpBody: true,
-        httpUrlBlocklist: ['http://localhost'],
-        autoStart: true,
-        traceSamplingRate: 1,
-        samplingRateForErrorFreeSessions: 1,
-        layoutSnapshotWidgetTypes: {
-          MyApp: 'MyApp',
-          MainScreen: 'MainScreen',
-        }),
+      enableLogging: true,
+      trackScreenshotOnCrash: true,
+      trackHttpHeaders: true,
+      trackHttpBody: true,
+      httpUrlBlocklist: ['http://localhost'],
+      autoStart: true,
+      traceSamplingRate: 1,
+      samplingRateForErrorFreeSessions: 1,
+      layoutSnapshotWidgetTypes: msrWidgetsForLayoutSnapshot,
+    ),
     clientInfo: ClientInfo(
-      apiKey:
-          "msrsh_0c89033fc9ca86c29ba0300452d65ee441a60aac5adc7c5ee2d5057ebcbb4133_2d215ff0",
+      apiKey: "msrsh_0c89033fc9ca86c29ba0300452d65ee441a60aac5adc7c5ee2d5057ebcbb4133_2d215ff0",
       apiUrl: "https://staging-ingest.measure.sh",
     ),
   );